Immunohistochemistry Troubleshooting Guide
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High background staining in immunohistochemistry (IHC) is commonly caused by insufficient blocking, nonspecific antibody binding, inadequate washing, endogenous enzyme activity, or tissue autofluorescence. Optimizing blocking conditions, antibody dilution, washing steps, and fluorescence settings can help reduce nonspecific staining and improve IHC signal specificity.
Possible Causes What You Can Do Insufficient blockingSelect appropriate serum as blocking buffer. Blocking for 1 hour at room temperature Interference from endogenous enzymesPerform H2O2 or Levamisole quenchingNon-specific binding from primary antibodies Dilute primary or secondary antibody. Choose another IHC-validated primary antibodiesInadequate washingIncrease washing cycles/time. Increase salt/detergent concentration
for stronger washesNon-specific binding from secondary antibodies Perform secondary antibody incubation only. Use pre-adsorbed secondary antibody Non-specific binding from chromogen Perform chromogen incubation only. Use other chromogen if necessary Interference from secondary antibody in multicolor staining Make sure that the fluorochrome does not overlap with one another. Autofluorescence issue Make sure that there is no endogenous background caused by tissue itself. Check under fluorescence microscope prior to staining to identify autofluorescence -
Poor or disrupted tissue morphology in IHC is most commonly caused by overly harsh antigen retrieval, tissue sections peeling off the slide, sectioning issues, or autolysis from delayed fixation. To preserve tissue morphology, optimize antigen retrieval conditions, dry sections at 60°C for 2–4 hours before staining, cut sections at 3–5 μm using a sharp blade, and fix tissue samples as quickly as possible after collection to prevent autolytic degradation.
Possible Causes What You Can Do Antigen retrieval too harshOptimize retrieval steps to give the best morphology. Tissue sections peeled off slide Dry samples for 2-4 hours at 60°C.
Tissue with high lipid content (eg breast tissues) should be dried for longer time.Sectioning issue Cut thinner slides for better resolution: 3-5 μm. Use a new/sharper blade.Autolysis has occurredFix samples as soon as possible.
Choose other fixatives to accelerate penetration.
Fixative perfusion might be necessary for larger tissues. -
Weak or no signal IHC staining is commonly caused by improper fixation, insufficient antigen retrieval, permeabilization issues, incompatible antibodies, or low target protein expression in tissue samples. Optimizing fixation conditions, antibody selection, antigen retrieval, and tissue preparation can help improve immunohistochemistry signal detection and staining intensity.
Possible Causes What You Can Do Over fixationReduce fixation time. Perform antien retrieval to unmask epitopes. Insufficient fixation Increase fixation time or try other fixative. Fixation process delayed Fix immediately as tissue is extracted. Permeabilization issueFor nuclear/cytoplasmic proteins, add permeabilization agent (eg Triton X-100, Saponin) in blocking and antibody incubation buffer.
For membrane/tight junction proteins, avoid permeabilization agent.Primary antibodies not suitable for IHCChoose an IHC-validated primary antibodies.Wrong secondary antibody usedMake sure that primary and secondary antibodies match one another. Low expression of protein in tissue samples Use signal amplification methods (eg: HRP Polymer ARG80982, ARG80967, ARG80966) Insufficient deparafinization Make sure that parafin is removed completely before staining.